linux-kernel - Re: [PATCH 5/5] mm/vmscan: fix misleading comment in isolate_lru

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Date:   Mon, 12 Jul 2021 09:28:21 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org, vbabka@...e.cz,
        axboe@...nel.dk, iamjoonsoo.kim@....com, alexs@...nel.org,
        apopple@...dia.com, willy@...radead.org, minchan@...nel.org,
        david@...hat.com, shli@...com, hillf.zj@...baba-inc.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] mm/vmscan: fix misleading comment in
 isolate_lru_pages()

On Sat 10-07-21 18:03:29, Miaohe Lin wrote:
> We couldn't know whether the page is being freed elsewhere until we failed
> to increase the page count.

This is moving a hard to understand comment from one place to another.
If anything this would benefit from what that elsewhere might be
typically or simply drop the comment altogether.

> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/vmscan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a74760c48bd8..6e26b3c93242 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1891,7 +1891,6 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  		 */
>  		scan += nr_pages;
>  		if (!__isolate_lru_page_prepare(page, mode)) {
> -			/* It is being freed elsewhere */
>  			list_move(&page->lru, src);
>  			continue;
>  		}
> @@ -1901,6 +1900,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  		 * page release code relies on it.
>  		 */
>  		if (unlikely(!get_page_unless_zero(page))) {
> +			/* It is being freed elsewhere. */
>  			list_move(&page->lru, src);
>  			continue;
>  		}
> -- 
> 2.23.0

-- 
Michal Hocko
SUSE Labs